Chemical mechanical polishing apparatus and method

ABSTRACT

A chemical mechanical polishing apparatus is provided. The chemical mechanical polishing apparatus includes a polishing pad, a pad conditioner, a measurement tool, and a controller. The polishing pad is provided in a processing chamber for polishing a wafer placed on the polishing surface of the polishing pad. The pad conditioner is configured to condition the polishing surface. The measurement tool is provided in the processing chamber and configured to measure the downward force of the pad conditioner. The controller is coupled to the pad conditioner and the measurement tool, and is configured to adjust the downward force of the pad conditioner in response to an input from the measurement tool.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority of U.S. Provisional PatentApplication No. 62/589,802, filed on Nov. 22, 2017, the entirety ofwhich is incorporated by reference herein.

BACKGROUND

Chemical Mechanical Polishing (CMP) is one type of processing used inthe manufacture of semiconductor devices. CMP is a process used tosmooth and planarize the surfaces of wafers using a combination ofchemical and mechanical forces. Integrated circuit (IC) dies in waferform are placed into a chamber of a CMP apparatus and are planarized orpolished at various stages of the CMP process. CMP processes may be usedto form planar surfaces on dielectric layers, semiconductor layers, andconductive material layers of a wafer, for example.

CMP apparatuses typically include a rotatable platen with a polishingpad attached thereto. In some CMP processes, a semiconductor wafer isplaced upside down against the polishing pad using a predeterminedamount of pressure. A liquid dispersion referred to as slurry, whichcontains chemicals and microabrasive grains, is applied to the polishingpad during the CMP process while the wafer is held against the rotatingpolishing pad. The wafer is also rotated in some applications. A padconditioning process can be carried out either during the polishingprocess or after the polishing process, to remove polished debris fromthe pad/polishing surface to improve the lifespan of the polishing pad.

Although existing apparatuses and methods for a CMP process have beengenerally adequate for their intended purposes, they have not beenentirely satisfactory in all respects. Consequently, it would bedesirable to provide a solution for polishing wafers in CMP apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages of the present disclosure, reference is now made to thefollowing descriptions taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 schematically illustrates a Chemical Mechanical Polishing (CMP)apparatus in accordance with some embodiments.

FIG. 2 schematically illustrates a pad conditioner that is movablebetween a conditioning position and a home position, and a measurementtool is provided beneath the pad conditioner at the home position formeasuring the downward force thereof, in accordance with someembodiments.

FIG. 3 schematically illustrates the internal configuration of ameasurement tool in accordance with some embodiments.

FIG. 4A schematically illustrates the top view of a part of ameasurement tool in accordance with some embodiments.

FIG. 4B schematically illustrates the top view of a part of ameasurement tool in accordance with some embodiments.

FIG. 5 is a simplified flow chart of a CMP method in accordance withsome embodiments.

FIG. 6 is a diagram plotting downward force measurements in a CMPapparatus versus process time of a continuous CMP process, a targetvalue, upper control limits and lower control limits, in accordance withsome embodiments

FIG. 7 schematically illustrates the internal configuration of apolishing head in accordance with some embodiments.

FIG. 8 schematically illustrates the bottom view of the polishing headin FIG. 7.

FIG. 9 schematically illustrates that the retaining ring of thepolishing head has a porous structure in accordance with someembodiments.

FIG. 10 is a cross-sectional view taken along the line B-B in FIG. 8.

FIG. 11 schematically illustrates that a washing solution supply systemis coupled to the polishing head, and the polishing head performs aself-cleaning process while it moves over the wafer load/unload stationafter the polishing process.

FIG. 12 schematically illustrates the stage body of a stage unit of awafer load/unload station having a plurality of spraying nozzles inaccordance with some embodiments.

FIG. 13 is a cross-sectional view of a spraying nozzle in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed. Various featuresmay be arbitrarily drawn in different scales for the sake of simplicityand clarity.

Furthermore, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

FIG. 1 schematically illustrates a perspective view of a part of aChemical Mechanical Polishing (CMP) apparatus 10 in accordance with someembodiments of the present disclosure. The CMP apparatus 10 is used topolish the top surface or device side of a semiconductor wafer (notshown in FIG. 1) during the fabrication of semiconductor devices on thewafer. A wafer is planarized or smoothed one or more times by the CMPapparatus 10 during a CMP process in order for the top surface of thewafer to be as flat as possible. The wafer may be a production wafer ora test wafer, for example. In accordance with some embodiments, thewafer has diameter in a range from about 150 millimeters (mm) to about450 mm, or even a larger diameter.

The CMP apparatus 10 includes a processing chamber 11 which provides asealed, contained system for the components of the CMP apparatus 10 asdescribed below. One or more load ports (not shown) can be coupled tothe chamber wall of the processing chamber 11 for allowing one or morewafers to enter and exit the CMP apparatus 10. The wafers in theprocessing chamber 11 can be transferred onto and off a waferload/unload station 12 using a robotic wafer transfer system (notshown). The wafer load/unload station 12 is used for the loading andunloading wafers of onto and from a wafer polishing station 13 that isused for chemically and mechanically polishing material layers on thewafers. As shown in FIG. 1, the wafer polishing station 13 includes apolishing platen 14, a polishing pad 15, a polishing head 16, a slurrydispenser 17, and a pad conditioner 18.

The slurry dispenser 17 is operable to dispense slurry S onto thepolishing pad 15 during the CMP process. The slurry S includes reactivechemicals that can react with the top surface of the wafer. Furthermore,the slurry S includes abrasive particles for mechanically polishing thewafer. In accordance with some embodiments, the slurry dispenser 17 iscoupled to a reservoir (not shown) that holds a supply of the slurry S.Moreover, the slurry dispenser 17 comprises a nozzle for dispensing theslurry S and a pivotable arm coupled to the nozzle. The pivotable arm isdriven by a mechanism, such as a motor (not shown), and hence the slurrydispenser 17 can be moved towards the polishing pad 15 during the CMPprocess (as shown in FIG. 1) and away from the polishing pad 15 afterthe CMP process.

The polishing pad 15 is formed of a material that is hard enough toallow the abrasive particles in the slurry S to mechanically polish thewafer, which is placed under the polishing head 16, during the CMPprocess. On the other hand, the polishing pad 15 is also soft enough sothat it does not substantially scratch the wafer. In accordance withsome embodiments, the polishing pad 15 is attached to the polishingplaten 14 by an adhesive film, adhesive, or glue, for example. Duringthe CMP process, the polishing platen 14 is rotated by a mechanism, suchas a shaft coupled a rotating motor (not shown), and hence the polishingpad 15 fixed thereon is also rotated along the polishing platen 14.

The polishing head 16 is configured to hold and move a wafer in variousstages of the CMP process. For example, as a wafer to be polished istransferred into the processing chamber 11 and moved onto the waferload/unload station 12, the polishing head 16 is driven by a mechanism,such as a pivotable arm and a motor (not shown), to move over the wafer.The wafer is then picked up by the polishing head 16. In accordance withsome embodiments, the polishing head 16 includes a plurality of airpassages (not shown), in which a vacuum may be generated. By vacuumingthe air passages, the wafer is sucked up and held on the bottom of thepolishing head 16 for the transportation of the wafer to the polishingpad 15. After the polishing of the wafer on the polishing pad 15 iscompleted, the polished wafer is further moved by the polishing head 16from the polishing pad 15 to the wafer load/unload station 12 so that itis ready to be transferred out of the processing chamber 11.

During the CMP process, the polishing head 16 is also operable toprovide a predetermined amount of pressure to press the wafer againstthe polishing pad 15 for mechanical polishing. For example, after thepolishing head 16 is moved over and also pressed against the polishingpad 15, the vacuuming in the air passages is then turned off, and hencethe wafer is no longer sucked up. Afterwards, a flexible membrane (notshown) disposed between the bottom of the polishing head 16 and thewafer is inflated, for example, by pumping air into zones in theflexible membrane, and hence the inflated flexible membrane presses thewafer against the polishing pad 15.

During the CMP process, the polishing head 16 is also rotated by amechanism, such as a shaft coupled a rotating motor (not shown), causingthe rotation of the wafer affixed to the polishing head 16. Inaccordance with some embodiments, as shown in FIG. 1, the polishing head16 and the polishing pad 15 rotate in the same direction (clockwise orcounter-clockwise). In accordance with alternative embodiments, thepolishing head 16 and the polishing pad 15 rotate in oppositedirections. With the rotation of the polishing pad 15 and the polishinghead 16, the slurry S flows between the wafer and the polishing pad 15through surface grooves (not shown) formed on the polishing surface 15Aof the polishing pad 15. Through the chemical reaction between thereactive chemicals in the slurry S and the top surface of the wafer, andfurther through the mechanical polishing (i.e. through contact andfriction between the top surface of the wafer and the polishing surface15A), the top surface of the wafer is planarized.

While not shown in FIG. 1, a circular retaining ring 161 (see FIGS. 7and 8) is provided along the periphery of the bottom of the polishinghead 16 and will be pressed against the polishing surface 15A during theCMP process. The retaining ring 161 is used to retain the wafer W (FIG.7) in case the wafer W becomes offset from the central axis of thepolishing head 16, so that the wafer W is not spun off from thepolishing pad 15 during the polishing process. The bottom surface of theretaining ring 161 may have some grooves G which allow the slurry S toget in and out of the retaining ring 161 during the rotation of thepolishing head 16 (and the retaining ring). In accordance with someembodiments, the retaining ring 161 comprises a wear-resistant material,which may be plastic, ceramic, polymer, etc. For example, the retainingring 161 is formed of polyphenylene sulfide (PPS), polyetheretherketone(PEEK), or a mix of these materials and other materials such as polymers(for example, polyurethane, polyester, polyether, or polycarbonate).

The pad conditioner 18 is configured and operable to perform aconditioning process to remove polished debris and undesirableby-products from the polishing surface 15A of the polishing pad 15during the CMP process. In accordance with some embodiments, the padconditioner 18 includes a conditioning disk 18A (see FIG. 2) includingembedded or encapsulated cut diamond particles on a substrate. Theconditioning disk 18A comes into contact with the polishing surface 15A(for performing the conditioning process) when the polishing pad 15 isto be conditioned, for example, during the polishing process aspreviously discussed or after the polishing process. During theconditioning process, both the polishing pad 15 and the conditioningdisk 18A rotate, and the conditioning disk 18A also sweeps back andforth across the polishing surface 15A, so that the protrusions orcutting edges of the conditioning disk 18A move relative to thepolishing surface 15A, thereby removing polished debris and undesirableby-products from the polishing surface 15A and re-opening the surfacegrooves on the polishing surface 15A (i.e. re-texturizing the polishingsurface 15A). Consequently, the cleanliness of the polishing surface 15Ais maintained and the lifetime of the polishing pad 15 is prolonged.

In accordance with some embodiments, as shown in FIG. 2, theconditioning disk 18A is mounted on one end of a pivotable arm 18B, anda driving shaft 18C is coupled to the other end of the pivotable arm 18Band a motor housing 18D. The motor housing 18D houses a rotating motor(not shown) that is used to drive the driving shaft 18C to rotate alongthe central axis A, so that the pivotable arm 18B and the conditioningdisk 18A can sweep back and forth across the polishing surface 15A(FIG. 1) during the CMP process. In addition, transmission assemblies(not shown) including a belt, pulleys, and the like, for example, areprovided in the driving shaft 18C and pivotable arm 18B, and hence therotating motor in the motor housing 18D can also drive the conditioningdisk 18A to rotate over the polishing surface 15A through thetransmission assemblies, during the CMP process.

In accordance with some embodiments, as shown in FIG. 2, theconditioning disk 18A and the pivotable arm 18B driven by the drivingshaft 18C are movable between a conditioning position P1 over thepolishing surface 15A and a home position P2 away from the polishingsurface 15A. The pad conditioner 18 performs the conditioning process asdescribed above to condition the polishing surface 15A at theconditioning position P1 and parks or rests at the home position P2after the conditioning process (e.g. at the interval between polishingprocesses of two successive wafers).

In accordance with some embodiments, the pad conditioner 18 also appliesdownward force to the polishing surface 15A to condition the polishingsurface 15A at the conditioning position P1, according to apredetermined downward force (value) indicated by a controller (whichwill be described later). For example, the pivotable arm 18B is bentdownward by a pressured air system (not shown) or similar actuatingdevices controlled by the controller, so that the conditioning disk 18Ais pressed against the polishing surface 15A to apply downward force tocondition the polishing surface 15A. It should be noted that thedownward force of the pad conditioner 18 is an important processingfactor which may affect the roughness and cleanliness of the polishingsurface 15A, as well as the polishing rate (also known as the CMP rate)of the CMP apparatus 10. When the downward force of the pad conditioner18 (i.e., the downward force actually applied by the pad conditioner) isunstable during the continuous CMP process, difficulty in controllingthickness of the polished layers on the wafers can result. Furthermore,the debris removal efficiency of the pad conditioner 18 is also reducedwhich may cause the polished debris or undesirable by-products remainedon the polishing surface 15A to re-stain on the wafers, resulting indefects on the wafers after the CMP process.

To monitor the downward force of the pad conditioner 18 (i.e., thedownward force actually applied by the pad conditioner) during the CMPprocess, a measurement tool 19 is provided in the processing chamber 11.In accordance with some embodiments, as shown in FIG. 2, the measurementtool 19 is disposed beneath the pad conditioner 18 at the home positionP2. Once the conditioning process is completed and the pad conditioner18 moves back to the home position P2, the pad conditioner 18 can applydownward force to the measurement tool 19 according to the predetermineddownward force value indicated by the controller, and the measurementtool 19 determines the downward force actually applied by the padconditioner 18 accordingly. Afterwards, the measurement tool 19 providesthe detected downward force information to a controller 20 (e.g. a faultdetection and classification system) coupled to the measurement tool 19and pad conditioner 18, and the controller 20 can adjust the downwardforce of the pad conditioner 18 in response to the input from themeasurement tool 19, which will be illustrated in more detail later.Therefore, the pad conditioner 18 can have a stable downward forceduring the continuous CMP process and the yield of the CMP process isalso improved.

FIG. 3 schematically illustrates the internal configuration of themeasurement tool 19 in accordance with some embodiments. FIG. 4Aschematically illustrates the top view of a part of the measurement tool19 in accordance with some embodiments. As shown in FIG. 3 and FIG. 4A,the measurement tool 19 includes a holder 191, a frame 192, a button193, a spring 194, and a pressure transducer 195. It should beappreciated that some additional elements can be added into themeasurement tool 19, and some of the elements described below can bereplaced or eliminated in other embodiments of the measurement tool 19.

The holder 191 is configured to support the components of themeasurement tool 19 in the processing chamber 11 (FIG. 2). The frame 192is disposed over the holder 191 and configured to receive the pressuretransducer 195 therein to prevent the pressure transducer 195 from beingexposed to the wet and corrosive environment in the processing chamber11. In accordance with some embodiments, as shown in FIG. 3, a receivingspace 192A (e.g. a recess) is formed in the frame 192 by mechanicaldrilling, for example, and the pressure transducer 195 is fixedlydisposed at the bottom of the receiving space 192A. The button 193 isinstalled in the receiving space 192A and exposed from the frame 192 tobe pressed by the pad conditioner 18 (as depicted by the downward arrowin FIG. 3). The width of the button 193 may be substantially the same asthat of the receiving space 192A so as to cover the receiving space 192Aby the button 193. In addition, the sidewall of the receiving space 192Acan guide the movement of the button 193 in the receiving space 192A.The spring 194 (e.g. a compression spring) is disposed between andconnects to the button 193 and the pressure transducer 195.

With the above configuration, when the pad conditioner 18 presses downthe button 193 at the home position P2 (FIG. 2), the pressure transducer195 can detect the downward force of the pad conditioner 18 based on thepressure from the button 193 and also provides an electric signalrelated to the amount of the downward force of the pad conditioner 18 tothe controller 20. The pressure transducer 195 may comprise variousconventional pressure transducers (e.g. pressure-electric type) that canconvert a certain value of pressure into its corresponding electricaloutput signal. The spring 194 can then push the button 193 upward backto the original position after the downward force from the padconditioner 18 is released.

FIG. 4B schematically illustrates the top view of a part of themeasurement tool 19 in accordance with other some embodiments. As shownin FIG. 4B, multiple buttons 193 are provided and exposed from the frame192 to be pressed by the pad conditioner 18 at the same time.Accordingly, the downward force of the pad conditioner 18 is evenlyapplied to the pressure transducer 195 via the buttons 193, and hencethe measurement result of the pressure transducer 195 is more accurate.However, it should be noted that the buttons 193 may have otherarbitrary numbers and arrangement patterns and are not limited to theembodiments in FIG. 4B.

In accordance with some embodiments, as shown in FIG. 3, the exposedsurface of the frame 192 is coated with a protection layer 196comprising an anti-corrosive material (for example, quartz, ceramic, orthe like), to protect the frame 192 (e.g. made of stainless steel or thelike) from the corrosive environment in the processing chamber 11. Whilenot shown, the exposed surface of the button 193 (e.g. made of metal orplastic) is also coated with the protection layer 196 for protecting thebutton 193. In addition, at least one airflow channel 192B may beprovided in the frame 192 to direct gas (e.g. inert gas) to pass throughthe pressure transducer 195 for removing excessive humidity which entersthe frame 192 and keeping the pressure transducer 195 dry. While notshown, one end of the airflow channel 192B is coupled to a gas supplyand the other end of the airflow channel 192B is coupled to an exhaustsystem. In accordance with some embodiments, a gas seal (not shown) madeof rubber or the like may also be provided between the button 193 andthe sidewall of the receiving space 192A to reduce the amount ofcorrosive gas or humidity that enters into the frame 192. Accordingly,the measurement tool 19 is suitable for being disposed in the processingchamber 11 to monitor the downward force of the pad conditioner 18during the CMP process.

FIG. 5 is a simplified flow chart of a CMP method 50 in accordance withsome embodiments. For illustration, the flow chart will be describedalong with the drawings shown in FIGS. 1, 2, and 6. Some of theoperations described below can be replaced or eliminated in differentembodiments. Alternatively, some operations may be added in differentembodiments.

The CMP method 50 includes operation 51, in which a batch ofsemiconductor wafers (not shown in the figures) are sequentiallypolished on a polishing surface 15A of a polishing pad 15 in a CMPapparatus 10 during a CMP process, as shown in FIG. 1. During the CMPprocess, each wafer is held by a polishing head 16 in contact with andto be pressed against the polishing surface 15A for mechanical polishingas previously described. At the same time, a slurry dispenser 17supplies slurry S onto the polishing surface 15A to create chemicalreaction effect and mechanical polishing effect to achieve theplanarization of the wafers.

The CMP method 50 further includes operation 52, in which a conditioningprocess is performed by a pad conditioner 18 to condition the polishingsurface 15A, as shown in FIG. 1. During the conditioning process, thepad conditioner 18 sweeps back and forth across the polishing surface15A for conditioning the polishing surface 15A. In addition, throughdriven by a pressured air system (not shown) or similar actuatingdevices, and according to the predetermined downward force valueindicated by the controller, the pad conditioner 18 also appliesdownward force to condition the polishing surface 15A. In accordancewith some embodiments, the conditioning process is performed during thepolishing process of each of the wafers, i.e. known as concurrentconditioning, or after the polishing process of each of the wafers.

The conditioning process is typically performed in order to removepolished debris and undesirable by-products from the polishing surface15A generated during the CMP process to maintain a consistent polishingrate of the polishing pad 15. However, although the controller hasindicated a predetermined downward force, the downward force actuallyapplied by the pad conditioner 18 may change (for example, an airleakage of the pressured air system may cause the downward force of thepad conditioner 18 to vary) during the continuous CMP process, so thatthe yield of the CMP process is adversely affected.

The CMP method 50 further includes operation 53, in which the downwardforce actually applied by the pad conditioner 18 is monitored during theCMP process by a measurement tool 19 provided in the processing chamber11 of the CMP apparatus 10, as shown in FIG. 2. In accordance with someembodiments, after the conditioning process is completed, the padconditioner 18 will move back to its home position P2 and wait for thenext conditioning process. The measurement tool 19 is provided beneaththe pad conditioner 18 at the home position P2 and configured to measurethe downward force actually applied by the pad conditioner 18 to obtaina measured downward force, and also generates an electric signal relatedto the amount of the measured downward force of the pad conditioner 18to a controller 20 (e.g. a fault detection and classification system),as described above.

In accordance with some embodiments, the measurement tool 19 measuresthe downward force of the pad conditioner 18 whenever the padconditioner 18 moves back to the home position P2 after the conditioningprocess (e.g. at the interval between polishing processes of twosuccessive wafers). In accordance with alternative embodiments, themeasurement tool 19 measures the downward force of the pad conditioner18 after a predetermined number of wafers have been polished, i.e. themeasuring frequency for the downward force of the pad conditioner 18 canbe predetermined and adjusted by users. In accordance with someembodiments, the controller 20 includes a computer and an I/O interface(not shown) for users to set up the measurement parameters (e.g. themeasuring frequency).

The CMP method 50 further includes operation 54, in which the measureddownward force of the pad conditioner 18 from the measurement tool 19and a predetermined downward force are compared to determine whether adifference between the measured downward force and the predetermineddownward force exceeds a range of acceptable values. For example, beforethe measured downward force is analyzed by the controller 20 (or beforethe CMP process), the users may set up a predetermined target (downwardforce) value (for example, in pounds (lb)) and an allowable deviationvalue (for example, a few pounds), via the I/O interface, to thecontroller 20. In some embodiments, as shown in FIG. 6, upper controllimit (UCL) is set at the target value plus the allowable deviationvalue, and lower control limit (LCL) is set at the target value subtractthe allowable deviation value. The difference between the UCL and LCC isreferred to as the range of acceptable values.

After the range of acceptable values for the difference between themeasured downward force and the predetermined downward force (e.g. thetarget value) is determined, the controller 20 compares the downwardforce of the pad conditioner 18 measured by the measurement tool 19 andthe predetermined downward force stored in the controller 20 todetermine whether the difference therebetween is within the range ofacceptable values.

After the comparison, if the difference between the measured downwardforce and the predetermined downward force is within (i.e. does notexceed) the range of acceptable values, the CMP method 50 repeatsoperations 51 to 54 until all semiconductor wafers S are processed.However, if the difference between the measured downward force and thepredetermined downward force exceeds the range of acceptable values (asdepicted by the circled portion in FIG. 6), the CMP method 50 continueswith operation 55, in which the controller 20 feedback controls, forexample, the pressured air system coupled to the pad conditioner 18, tocalibrate the downward force actually applied by the pad conditioner 18to the (predetermined) target downward force. Afterwards, the CMP method50 repeats operations 51 to 54 until all semiconductor wafers S areprocessed or further re-calibrates the downward force of the padconditioner 18 (i.e. operation 55) when the difference between themeasured downward force and the predetermined downward force exceeds therange of acceptable values again.

In accordance with alternative embodiments, the CMP method 50 mayfurther comprise an operation of indicating an alarm condition by thecontroller 20 when the calibration of the downward force of the padconditioner 18 occurs many times (for example, more than five times). Itshould be appreciated that the air leakage of the pressured air systemoccurs many times can indicate a fault or abnormality situation in thepressured air system. Therefore, the controller 20 triggers an alarmcondition and notifies the users of the CMP apparatus 10 to domaintenance or repair the abnormal pressured air system, so that the airleakage issue is remedied early.

As the downward force of the pad conditioner 18 can be dynamicallyadjusted by the controller 20, the debris removal efficiency of the padconditioner 18 remains consistent during the continuous CMP process.Therefore, the yield of the CMP process is improved (for example, thedefects on the wafers after the CMP process are reduced) and thelifetime of the polishing pad 15 is also prolonged. Furthermore, sincethe downward force of the pad conditioner 18 is detected while the padconditioner 18 parks at its home position, the CMP processing sequenceis not changed and the CMP processing time is not increased.

In the present disclosure, additional features can be provided intoembodiments of the CMP apparatus 10 in order to reduce polished debrisand undesirable by-products remained on the polishing surface 15A of thepolishing pad 15 (i.e. maintain the cleanliness of the polishing surface15A) during or after the CMP process.

For example, the retaining ring 161 of the polishing head 16 may furtherform a plurality of holes 161A on the bottom surface thereof that facesthe polishing surface 15A (FIG. 1), as shown in FIGS. 7 and 8. Inaddition, at least one fluid channel 162 is provided in the polishinghead 16 and fluidly connects to the holes 161A and an exhaust system 163(e.g. comprising a vacuum pump) that can produce vacuum suction. Byvacuuming the fluid channel 162 as the retaining ring 161 is pressedagainst the polishing surface 15A, polished debris and CMP by-productscan also be removed from the polishing surface 15A via the holes 161A,in addition to the sweeping removal performed by the pad conditioner 18.Therefore, it can improve the cleanliness of the polishing surface 15Aand reduce the chance of polished debris and undesirable by-productsremaining on the polishing surface 15A to re-stain on the wafer W duringthe CMP process.

In accordance with some embodiments, the holes 161A are formed on theretaining ring 161 by mechanical drilling or other available techniques.The holes 161A may be circular, triangular, square, elliptical, oranother shape. In accordance with some embodiments, the holes 161A arearranged on the circular retaining ring 161 in a regular (for example,with a uniform hole-to-hole interval) or irregular manner. In addition,the size of the holes 161A may be chosen so that aggregated debris orparticles remaining on the polishing surface 15A can be successfullyremoved. In accordance with some embodiments, the fluid channel 162 is apipeline arranged in a circle to connect to the holes 161A.

In accordance with alternative embodiments, the holes 161A may beomitted, and the retaining ring 161 is formed of a porous materialcontaining pores that allow fluid to pass through, as shown in FIG. 9.The fluid channel 162 provided in the polishing head 16 also fluidlyconnects the retaining ring 161 and the exhaust system 163. In this way,polished debris and CMP by-products can also be removed from thepolishing surface 15A by vacuum suction via the pores in the retainingring 161, in addition to the sweeping removal performed by the padconditioner 18. The retaining ring 161 having a porous structure may beformed by sintering or another available technique.

In accordance with some embodiments, as shown in FIG. 10, the edges E ofthe retaining ring 16 which may contact the polishing surface 15A(FIG. 1) during the polishing process are further designed as curvedshapes (such as round or arc shape), in order to reduce damage to theretaining ring 16 due to the friction between the polishing surface 15Aand the retaining ring 16. Therefore, polished debris and undesirableby-products generated during the CMP process can also be reduced.

In accordance with some embodiments, as shown in FIG. 11, a washingsolution supply system 164 (e.g. comprising a pump and a reservoir forholding a washing solution) is further provided to fluidly connect thefluid channel 162 in the polishing head 16. After the polishing process,the washing solution supply system 164 is used to supply a washingsolution, such as de-ionized water or another available chemicalcleaner, to flow though the fluid channel 162 and exit the polishinghead 16 from the holes 161A on the retaining ring 161, so as to cleanthe fluid channel 162 and prevent contaminants (i.e. polished debris andCMP by-products) from accumulating in the fluid channel 162.Accordingly, it can reduce the chance that the contaminants in the fluidchannel 162 will move back to the polishing surface 15A.

In accordance with some embodiments, the polishing head 16 performs theabove self-cleaning process to clean the fluid channel 162 while itmoves over the wafer load/unload station 12 after the polishing process.As shown in FIG. 11, the wafer load/unload station 12 includes a tank122 configured to collect the dirty washing solution from the polishinghead 16. One port 122A is provided on the bottom of the tank 122 andcoupled to a discharge system for removing the washing solution in thetank 122. A stage unit 121 is also provided in the tank 122 andconfigured for the loading and unloading of wafers W onto and from thepolishing pad 15 via the polishing head 16, as described above. Whilenot shown, the stage unit 121 is driven by a mechanism, such as a Z-axismotor, to transfer a wafer W to the polishing head 16 or receive a waferW transferred from the polishing head 16.

In accordance with some embodiments, as shown in FIGS. 11 and 12, thestage body 121A of the stage unit 121 includes a plurality of sprayingnozzles N that are used to supply a washing solution (e.g. de-ionizedwater or another available chemical cleaner) to clean the wafer W andthe retaining ring 161 of the polishing head 16. In other words, thestage unit 121 can also serve as a clean unit for cleaning the polishedsurface of the wafer W and the retaining ring 161 after the CMP process.While not shown, the spraying nozzles N may be retracted into the stagebody 121A (i.e. does not protrude above the surface of the stage body121A) while a wafer W is ready to be placed on the stage body 121A.

In accordance with some embodiments, as shown in FIG. 12, the stage body121A includes a circular inner portion 1210 and an annular outer portion1212 surrounding the inner portion 1210. The diameter of the innerportion 1210 may correspond to that of the wafer W (FIG. 11), and theouter diameter of the outer portion 1212 may correspond to that of theretaining ring 161 (FIG. 11). The spraying nozzles N are provided in theinner portion 1210 and outer portion 1212. In accordance with someembodiments, the spraying nozzles N are evenly distributed in the innerportion 1210 and outer portion 1212, as shown in FIG. 12, for example.The number and position of the spraying nozzles N are chosen so that thespraying nozzles N can dispense a washing solution onto the entire waferW and the retaining ring 161.

While not shown, the spraying nozzles N are coupled to a washingsolution supply system via at least one pipeline or tube provided in thestage body 121A. In addition, a heater (not shown) may also be providedin the stage body 121A in some embodiments, in order to heat the washingsolution flowing through the pipeline, so that the heated washingsolution supplied by the spraying nozzles N has a desirable temperaturefor effectively removing the contaminants on the wafer W and theretaining ring 161. The spraying nozzles N may comprise ceramics,quartz, or any other anti-corrosive materials (such as plastic).However, it should be appreciated that many variations and modificationscan be made to the embodiments of the disclosure.

In accordance with some embodiments, the outer portion 1212 is rotatablewith respect to the inner portion 1210 (i.e. the outer portion 1212 canrotate along the central axis of the stage body 121A while the innerportion 1210 is fixed), so that the spraying nozzles N in the outerportion 1212 can clean the entire retaining ring 161 (and all thegrooves G (see FIG. 8)) to reduce contaminants remained on the retainingring 161. The outer portion 1212 may be rotated by a rotating motor,gears, and the like in some embodiments.

In accordance with some embodiments, the spraying direction of eachspraying nozzle N is arranged so that the spraying nozzles N candispense a washing solution onto the entire wafer W and the retainingring 161 (i.e. the spraying direction of each spraying nozzle N can beadjusted to be vertical or inclined by any angle with respect to thewafer W and the retaining ring 161 based on actual requirements, and thespraying nozzles N may have different spraying directions). Inaccordance with alternative embodiments, the stage unit 121 furtherincludes a plurality of rotation motors M provided in the stage body121A and coupled to the spraying nozzles N. The rotation motors M cancontrol the spraying direction of the respective spraying nozzle N (e.g.allow the spraying nozzles N, either in the inner portion 1210 or theouter portion 1212, to spray a washing solution in a rotating manner, asshown in FIG. 12) to enlarge the spray region of each spraying nozzle N.

Various spraying shapes of the washing solution, including a jet shape,a fan shape, a mist shape, or the like, can also be generated by thespraying nozzles N. In accordance with some embodiments, as shown inFIG. 13, the spraying nozzle N has a rounded nozzle hole O, a firstinner path T1, and a second inner path T2 surrounding the first innerpath T1. The first inner path T1 is fluidly connected to a gas source inthe washing solution supply system (not shown) which is used to supplyN2 or other inert gas, and the second inner path T2 is fluidly connectedto a liquid source in the washing solution supply system (not shown).With this configuration, the washing solution sprayed by the nozzle holeO may have various spray shapes due to the mixing of the inert gas inthe first inner path T1 with the washing solution in the second innerpath T2. For example, the spraying nozzle N may spray the washingsolution with a fan shape (as shown in FIG. 13) when the gas source hasa medium pressure such as 50 to 250 psi. Alternatively, the sprayingnozzle N may spray the washing solution with a jet shape when the gassource has a higher pressure such as 250 to 1000 psi, or spray thewashing solution with a mist shape when the gas source has a lowerpressure such as 10 to 50 psi. However, it should be appreciated thatthe spraying nozzles N may also include several configurations and arenot limited to the embodiments described above.

The embodiments of the present disclosure have some advantageousfeatures: The CMP apparatus uses a measurement tool to monitor thedownward force of the pad conditioner while it moves back to the homeposition (e.g. at the interval between polishing processes of twosuccessive wafers) and a controller to feedback control and dynamicallycalibrate the downward force of the pad conditioner during thecontinuous CMP process in response to measurement result from themeasurement tool. Therefore, the debris removal efficiency of the padconditioner remains consistent during the continuous CMP process, andhence the polished debris and undesirable by-products can besuccessfully removed from the polishing pad during the CMP process andthe yield of the CMP process is also improved (e.g. the polishedthickness of a batch of wafers is consistent and the defects on thewafers are reduced). In addition, the polishing head can help to removethe polished debris and undesirable by-products from the polishing padvia the vacuum holes provided on the bottom surface of the retainingring. In addition, several spraying nozzles are provided on the stageunit of the wafer load/unload station to supply a washing solution toclean the polished head and the retaining ring of polishing head afterthe CMP process, and hence the yield of the CMP process is furtherimproved.

In some embodiments, a chemical mechanical polishing apparatus isprovided. The chemical mechanical polishing apparatus includes apolishing pad, a pad conditioner, a measurement tool, and a controller.The polishing pad is provided in a processing chamber for polishing awafer placed on the polishing surface of the polishing pad. The padconditioner is configured to condition the polishing surface. Themeasurement tool is provided in the processing chamber and configured tomeasure the downward force of the pad conditioner. The controller iscoupled to the pad conditioner and the measurement tool, and isconfigured to adjust the downward force of the pad conditioner inresponse to an input from the measurement tool.

In some embodiments, a chemical mechanical polishing apparatus isprovided. The chemical mechanical polishing apparatus includes apolishing pad, a polishing head, a pad conditioner, a measurement tool,and a controller. The polishing pad has a polishing surface. Thepolishing head is configured to hold a wafer in contact with thepolishing surface. The pad conditioner is configured to condition thepolishing surface. The measurement tool is disposed beneath the padconditioner at the home position and configured to measure the downwardforce of the pad conditioner. The controller is coupled to the padconditioner and the measurement tool, and configured to calibrate thedownward force of the pad conditioner when the difference between thedownward force and a predetermined downward force exceeds a range ofacceptable values.

In some embodiments, a chemical mechanical polishing method is provided.The method includes polishing a batch of wafers in sequence on apolishing surface of a polishing pad. The method further includesconditioning the polishing surface with a pad conditioner. The methodfurther includes measuring the downward force of the pad conditionerwhen the pad conditioner is at the home position. The method alsoincludes comparing the downward force and a predetermined downward forceto determine whether the difference between the downward force and thepredetermined downward force exceeds a range of acceptable values. Inaddition, the method includes calibrating the downward force of the padconditioner when the difference exceeds the range of acceptable values.

Although embodiments of the present disclosure and their advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims. For example, it will be readily understood by those skilled inthe art that many of the features, functions, processes, and materialsdescribed herein may be varied while remaining within the scope of thepresent disclosure. Moreover, the scope of the present application isnot intended to be limited to the particular embodiments of the process,machine, manufacture, composition of matter, means, methods and stepsdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the disclosure of the present disclosure,processes, machines, manufacture, compositions of matter, means,methods, or steps, presently existing or later to be developed, thatperform substantially the same function or achieve substantially thesame result as the corresponding embodiments described herein may beutilized according to the present disclosure. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.In addition, each claim constitutes a separate embodiment, and thecombination of various claims and embodiments are within the scope ofthe disclosure.

What is claimed is:
 1. A chemical mechanical polishing apparatus,comprising: a polishing pad provided in a processing chamber forpolishing a wafer placed on a polishing surface of the polishing pad; apad conditioner configured to move between a conditioning position overthe polishing surface and a home position away from the polishing padrather than over the polishing surface, wherein the pad conditioner isoperable to apply a downward force according to a predetermined downwardforce stored in a controller to condition the polishing surface at theconditioning position, and move from the conditioning position to thehome position after conditioning the polishing surface; a measurementtool provided separately in the processing chamber and disposed relativeto the pad conditioner at the home position, wherein the measurementtool is configured to measure the downward force actually applied by thepad conditioner to the measurement tool after conditioning the polishingsurface; and the controller coupled to the pad conditioner and themeasurement tool, and configured to adjust the downward force actuallyapplied by the pad conditioner to the predetermined downward force inresponse to an input from the measurement tool.
 2. The chemicalmechanical polishing apparatus as claimed in claim 1, wherein themeasurement tool includes a pressure transducer configured to measurethe downward force actually applied by the pad conditioner to themeasurement tool and provide an electric signal related to an amount ofthe measured downward force to the controller, and wherein thecontroller is configured to adjust the downward force actually appliedby the pad conditioner in response to the electric signal from themeasurement tool.
 3. The chemical mechanical polishing apparatus asclaimed in claim 2, wherein the measurement tool further includes aframe configured to receive the pressure transducer therein to preventthe pressure transducer from being exposed to environment in thechemical mechanical polishing apparatus.
 4. The chemical mechanicalpolishing apparatus as claimed in claim 3, wherein the measurement toolfurther includes a button exposed from the frame to be pressed by thepad conditioner and a spring connecting the button to the pressuretransducer.
 5. The chemical mechanical polishing apparatus as claimed inclaim 3, wherein a surface of the frame is coated with a protectionlayer.
 6. The chemical mechanical polishing apparatus as claimed inclaim 3, wherein an airflow channel is provided in the frame to directgas to pass through the pressure transducer.
 7. The chemical mechanicalpolishing apparatus as claimed in claim 1, further comprising apolishing head configured to hold the wafer in contact with thepolishing surface and including a retaining ring arranged along aperiphery of the polishing head, wherein a plurality of holes are formedon a surface of the retaining ring that faces the polishing surface. 8.The chemical mechanical polishing apparatus as claimed in claim 7,further comprising an exhaust system that connects to the holes via afluid channel provided in the polishing head.
 9. The chemical mechanicalpolishing apparatus as claimed in claim 1, further comprising apolishing head configured to hold the wafer in contact with thepolishing surface and including a retaining ring arranged along aperiphery of the polishing head, wherein the retaining ring comprisesporous material, and the chemical mechanical polishing apparatus furthercomprises an exhaust system that connects to the retaining ring via afluid channel provided in the polishing head.
 10. The chemicalmechanical polishing apparatus as claimed in claim 7, wherein edges ofthe retaining ring adjacent to the polishing pad are curved in avertical cross-sectional view.
 11. The chemical mechanical polishingapparatus as claimed in claim 8, further comprising a washing solutionsupply system that connects to the fluid channel.
 12. The chemicalmechanical polishing apparatus as claimed in claim 1, further comprisinga stage unit and a polishing head, wherein the polishing head isconfigured to transfer the wafer between the stage unit and thepolishing pad, and wherein the stage unit includes a plurality ofspraying nozzles configured to supply a washing solution to the waferand a retaining ring of the polishing head.
 13. The chemical mechanicalpolishing apparatus as claimed in claim 12, wherein the spraying nozzlesare disposed in an inner portion and an outer portion of the stage unit,and the outer portion is rotatable with respect to the inner portion.14. The chemical mechanical polishing apparatus as claimed in claim 12,wherein the stage unit further comprises a plurality of rotation motorsconfigured to control a spraying direction of the respective sprayingnozzle.
 15. A chemical mechanical polishing apparatus, comprising: apolishing pad having a polishing surface; a polishing head configured tohold a wafer in contact with the polishing surface; a pad conditionerconfigured to move between a conditioning position over the polishingsurface and a home position away from the polishing pad rather than overthe polishing surface, wherein the pad conditioner is operable to applya downward force according to a predetermined downward force stored in acontroller to condition the polishing surface at the conditioningposition, and move from the conditioning position to the home positionafter conditioning the polishing surface; a measurement tool disposedrelative to the pad conditioner at the home position and separated fromthe pad conditioner, wherein the measurement tool is configured tomeasure the downward force actually applied by the pad conditioner tothe measurement tool after conditioning the polishing surface; and thecontroller coupled to the pad conditioner and the measurement tool, andconfigured to compare the downward force measured by the measurementtool and the predetermined downward force, and calibrate the downwardforce actually applied by the pad conditioner when a difference betweenthe downward force measured by the measurement tool and thepredetermined downward force exceeds a range of acceptable values.
 16. Achemical mechanical polishing apparatus, comprising: a processingchamber; a polishing pad provided in the processing chamber and having apolishing surface; a pad conditioner configured to move between aconditioning position over the polishing surface and a home positionaway from the polishing pad rather than over the polishing surface,wherein the pad conditioner is operable to apply a downward forceaccording to a predetermined downward force stored in a controller tocondition the polishing surface at the conditioning position, and movefrom the conditioning position to the home position after conditioningthe polishing surface; a measurement tool provided separately in theprocessing chamber and disposed relative to the pad conditioner at thehome position, wherein the measurement tool is configured to measure thedownward force actually applied by the pad conditioner to themeasurement tool after conditioning the polishing surface, wherein themeasurement tool comprises: a frame, wherein an outer surface of theframe is coated with a protection layer to protect the frame from anenvironment in the processing chamber; and a pressure transducerreceived in the frame, configured to measure the downward force actuallyapplied by the pad conditioner to the measurement tool; and thecontroller coupled to the pad conditioner and the measurement tool, andconfigured to compare the downward force measured by the measurementtool and the predetermined downward force, and calibrate the downwardforce actually applied by the pad conditioner when a difference betweenthe downward force measured by the pressure transducer and thepredetermined downward force exceeds a range of acceptable values. 17.The chemical mechanical polishing apparatus as claimed in claim 16,wherein the measurement tool further comprises a button coupled to thepressure transducer and exposed from the frame to be pressed by the padconditioner.
 18. The chemical mechanical polishing apparatus as claimedin claim 16, further comprising: a polishing head configured to hold awafer in contact with the polishing surface, wherein a retaining ring isarranged along a periphery of the polishing head to keep the wafer inplace, wherein a plurality of holes are formed on a surface of theretaining ring that faces the polishing surface; and an exhaust systemcoupling to the holes via a fluid channel in the polishing head.
 19. Thechemical mechanical polishing apparatus as claimed in claim 18, whereinthe retaining ring is formed of a porous material.
 20. The chemicalmechanical polishing apparatus as claimed in claim 18, wherein the fluidchannel in the polishing head is closer to the exhaust system than theholes of the retaining ring in a vertical direction perpendicular to thesurface of the retaining ring.